1. Field of the Invention
The present invention is related to a manufacturing method for enhancing an ordered structure of block copolymers, and more particularly to a thermal annealing process for block copolymers having conducting polymers and rod segments.
2. Description of Related Art
Block copolymers having an ordered structure have been widely used in lithography, molecular films, optoelectronic devices, and solar cells by taking advantage of the ordered structure. For example, in solar cells, a highly-ordered continuous phase is essential for high photoelectric conversion efficiency.
Block copolymers having self-assembly properties can form a highly ordered and periodic nanostructure, which have attracted great interest in fields related to nanotechnology. For example, in addition to the traditional stacked, hexagonal packed, and body-centered cubic structures, more complex structures may be formed, such as porous structures, bi-continuous phase structures (gyroid, i.e. Ia3d symmetric structures), diamond structures and so on.
On the other hand, novel block copolymers are generally composed of rod-coil segments or rod-rod segments, or the types of segments are increased to form a tri-block copolymer, and even a multi-block copolymer. The molecular structure of the rod segment is difficult to twist or deform, and therefore has high planarity. However, the strong intermolecular π-π stacking or van der Waals force results in a very long annealing time and an overly high annealing temperature for such block copolymer molecules to be arranged into a highly ordered structure. The overly-high annealing temperature may even cause degradation of the block copolymer molecules. It has been reported that the problem can be solved by changing the chemical structure of the block copolymer, which however, deteriorates the application-associated properties, such as opto-electrical characteristics, charge conductivity and so on.
Therefore, it is a bottleneck to effectively reduce the time and temperature of the annealing process without changing the material structure per se. Therefore, the present invention provides a manufacturing method, wherein an additive, i.e., a small molecule additive, which is miscible with the block copolymer containing the rod segment, such that during the subsequent thermal annealing process, the small organic molecule may provide a solution-like environment to the rod segment, thereby reducing π-π interaction or van der Waals force. The small molecule additive may volatilize during the thermal annealing process or high vacuum condition without remaining in the block copolymers. As such, the ordered structure of the block copolymers is manufactured and the subsequent applications of the block copolymer can be maintained.